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Tolman Jumbo Skiff - Ken Chace's Blog


Tolman Jumbo - Tank installation

I installed a 52 gallon ‘belly’ tank mounted with its front right at station 6. The tank is 60” long, so extends quite a ways back. I did not want to raise the floor any more than necessary, so the tank fittings are slightly above floor level. I covered the fittings with a ‘curb’ or ‘chase’ that I will run the hoses in. The chase is 6” wide and 3” high. Before committing to it, I made sure it does NOT get in the way of standing up to steer or getting in and out of the cuddy. The tank sits right on the bottom of the boat and its V shape is an almost perfect match of the hull’s V shape.

I reinforced the area underneath the tank with a layer of 24oz biax that wraps all the way up onto the main stringers. I put a thin layer of polyethylene foam under the tank but none at the very center to allow water to drain (The tank is flat at this point too and so is no where near the boat bottom in the center). The front, back and sides of the tank compartment are padded with a thickness of foam to allow 2-3% expansion in all directions as required by the tank MFG. This foam is quite firm and is impervious to gas.

The plywood tank cover sits on plywood ledges on both sides and at the rear and is made of ¾ plywood, but is unsupported for almost 30” across. Since its part of the main walkway I had to stiffen it. (Its too close to the tank to add strips of wood underneath). So I epoxied 3 layers of 10oz glass on the underside for support and 1 layer of 10oz on top. This *completely* eliminated any bounce or sag when walking on the tank cover! In addition, the cover had a bit of a ‘bow’ in it. Before glassing the bottom of the cover, I screwed 2x4’s to the ‘topside’ to hold it flat. (I applied tiny pieces of masking tape to the screwheads so they wouldn’t get filled in. After the epoxy cured, I used a small forstner bit to drill the glass above the screws – which I will fill in later) After the 3 layers of bottom glass had cured for 3 days, I removed the 2x4’s and the plywood remained perfectly flat! Awesome.

Tolman Jumbo - stringer system

Finishing the bottom glassing after the hull was turned was straightforward and uneventful. After applying fillets and glass to the inner chine, I cut 12” wide strips of 24oz biax to use on both sides of the main stringers. Since the stringers were just a bit over 7” tall, this left a generous portion of glass to wrap down onto the bottom. I felt this gives a bit of extra strength where it can most be used – tying the hull to the stringers. Renn is right about soaking the 24oz biax with epoxy when he says to ‘pour it on’. It takes a LOT of epoxy to saturate that 24oz cloth. I applied the biax in 7’ long strips and this is about a long as I would want to do it alone. Coat the stringers first, then liberally apply the epoxy to the biax, put the biax on the stringer and bottom, roll it out with a bubble roller, then more epoxy on top and another firm rolling with the bubble roller. This gets the biax down nice and snug.

Finishing the hull

I used balua mahogany for the keel, keel strakes and splash rails. My thinking is that this wood is outside the ‘skin’ of the boat and much more likely to get some water into it. So I wanted a wood that was fairly tough and also rot resistant. This wood was VERY difficult to bend correctly on the keel at the bow and even the splash rails gave me a few fits – but I managed. I installed all of the pieces with 316 stainless screws. I realize that I could get crevice corrosion under certain circumstances, but I’m willing to deal with that when and if it happens. I did not use any UHMW on the boat. First of all because this is going to be used as a pleasure and recreational fishing boat. It should not be subjected to a lot of physical abuse and I will rarely beach it. If it turns out that I end up wearing any of those parts too much, the mahogany will make a good base to apply a thin piece of UHMW (3/8-1/2) on top to take the wear.

Tolman Jumbo - Sheathing the hull with glass

It took me a whole day – about 10 hrs - to glass the entire hull in 2 layers of 10oz cloth. This is more and heavier cloth than the book specs, but I feel this adds a lot of strength, puncture resistance and moisture protection. I wanted to do this all at once if at all possible because doing it all together would ensure the best possible adhesion between layers – wet on wet (I didn’t know for sure if it WAS possible to do it all in one day).

The first hour of the day was spent carefully cleaning the hull (and I found a couple of spots I missed when sanding). The next 10 hours I spent applying 8 sheets of 25 foot long x 38” or 50” wide cloth. I used 50” cloth on the bottom so it would over lap the ‘keel’ AND the chine, and I used 38” wide on the sides that overlapped the 50” bottom cloth. I applied the cloth using Renn’s method – wet the hull with epoxy first (for the first layer), roll the cloth onto the wet epoxy, then roll on more epoxy to almost fill the weave. The next layer went on right over the previously wet-out layer and it stuck well. Then more epoxy to wet out the second layer.

Tolman Jumbo - Gluing on the bottom and sides

Applying the second 1/4" layer to the bow went very smoothly. As Renn indicated in the book, I just had to plane a tiny sliver along a short section of each side to make the fit perfect. I applied unthickened epoxy to both sides, then a coating of somewhat thickened epoxy. I used huge numbers of screws and washers to ensure good contact. I applied the screws in the relative order that Renn recommends in the book and it worked great.

Next I installed side framing in locations to frame the approximate front and rear of my pilothouse, and added 2 more roughly centered within the open cockpit area. Those will be used later for mounting things like rod holders, etc.

Gluing the bottom to the transom and stringers

Gluing the bottom to the stringers, transom and bowstem was straightforward, but a major exercise in trying to work as fast as possible. It’s a lot of glue to apply, things to line up and screws to drive before the epoxy kicks off. Everything HAS to be dry fit first because there can be no changes once you start this. Make sure and cut the rear limber holes! It’s a bear to do afterwards.

I made sure that everyplace that glue would be applied was sanded for maximum epoxy holding power. I also marked glue lines on EVERY side of every location on the bottom where it would contact glue and snapped chalk lines on the bottom to mark where the screws would go into the stringers. These lines would guide me when I applied the epoxy and screws, and also help me line things up when I lowered the bottom so I wouldn’t smear the epoxy.

Tolman Jumbo - Stringers and shelves

Picked up the LVL stringer material and the special 1 1/8 flooring plywood that will be used for the front 16' of the shelves (Gunnels). The LVL beam is 14” X 1 3/4" X 20’ long and man is that beam heavy. It must weigh at least 100 lbs. My local lumber yard had a huge assortment of sizes right in stock, including the size I needed. The plywood was a different matter. One lumber yard said they never heard of it. They called their supplier and HE said he never heard of it either – great. Off to another place – had better luck there. That’s one thick sheet of plywood.

Tolman Jumbo - Fiberglassing the inside of the bottom

It's been a little while since I posted. I'll try to catch up my posts in the next few days.

The fiberglassing of the entire inside is done with 10oz cloth. The combination of fir marine plywood and 10oz cloth really sucks up the epoxy. I think it took about 20-24oz PER 38" wide strip (and this is run across the bottom - about 74" long for each strip) This all went pretty well, but since there is so much epoxy going on, it took me a lot longer than I thought it would. First a heavy coat of epoxy is rolled onto the mostly bare plywood. Then the (precut and pre-rolled onto sticks) fiberglass is rolled out onto the wet epoxy. I found out that one must carefully roll the fiberglass onto the wet epoxy, repositioning the fiberglass after it is rolled out is quite messy and difficult. Next a coat of epoxy is rolled into the glass. Each ‘strip’ of fiberglass is lapped an inch or so onto the previous one to give continuous strength and coverage. Now that the weather is warmer and its about 72 in my garage, I had to pause a couple of times to roll out the bubbles before previous strips set up too much. All together it took about 2-3 hours to do the entire inside of the bottom. I think it took 7 “strips” of fiberglass. The last one up at the bow was shorter but also took longer to put in because it has to be sliced in a couple of places to allow it to lie into the deep contours there. I ended up allowing it to lap over itself heavily. That’s ok though, I certainly don’t mind the extra layers up there. It’ll just give it that much more strength.

Sanding and Taping the chine shelves

All I can say is wow, does the bottom look great with all the clamps removed and all the joints sanded. I was very happy to discover that my old Porter Cable paint sander with a 20 grit disk is really great for sanding epoxy and blending lines. I was able to quickly sand all of the scarf and chine joints including the various drips, etc all with one disk and it still has some life in it yet! The only thing is that the constant leaning over the hull long enough to do the sanding takes its toll on your back.

I had previously used scissors to cut strips for fiberglass tape, but this time I tried using a razor knife and it definitely worked well. I think I might stay with using the razor knife for cutting tape because I don't think my rather inexpensive scissors will hold up and they're really useful in other situations.

June 12, cutting and attaching the chine flats

Spent some time off on Monday cutting out the chine flats, attaching and gluing to the bottom. This is a pretty straightforward operation and easier than some of the other things that I'd been doing in that the pieces were a lot smaller! Not only that, but I had help tracing the chine flats onto the plywood - my little girl wanted to help Daddy work on the boat!

I did run into one issue that I had to think about a bit before I was able to resolve it: In the book, Renn has you scarf together two pieces of 1/2" stock to make the curved forward chine flat section. This would put the first chine flat butt joint well behind the 1/4 to 1/2 transition. I used the simpler method of making 3 seperate 8' pieces. The forward piece has most of the curve to it, the second piece has just a small amount of the remaining curve and the 3rd piece is straight. The issue is that when using this method, the joint between the forward and 2nd piece falls very close to the scarf joint between the 1/4" and 1/2" bottom pieces. Since the 1/4 bends so much more easily then the 1/2", there is a tendency for the 1/4" to begin to bend almost immediately forward of the scarf. With the chine flat joints so close to this transition, the forward chine flat piece wants to be at the angle of the 1/4 bottom sheet and the 2nd chine flat piece wants to be at the angle of the 1/2 bottom sheet. This causes an abrupt angle change at the chine flat joint which does NOT look good since it interrupts the flowing curved line of the chine.

Best Marine Epoxy

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EpoxyUSA.com Progressive Basic No-Blush Epoxy

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